docs: def append(self, key, samples, sampling_rate):
          """
          Append the given samples to the data that already exists
          in the container for the given key.
  
          Args:
              key (str): A key to store the data for.
              samples (numpy.ndarray): 1-D array of audio samples (int-16).
              sampling_rate (int): The sampling-rate of the audio samples.
  
          Note:
              The container has to be opened in advance.
              For appending to existing data the HDF5-Dataset has to be chunked,
              so it is not allowed to first add data via ``set``.
          """
          if not np.issubdtype(samples.dtype, np.floating):
              raise ValueError('Samples are required as np.float32!')
  
          if len(samples.shape) > 1:
              raise ValueError('Only single channel supported!')
  
          existing = self.get(key, mem_map=True)
          samples = (samples * MAX_INT16_VALUE).astype(np.int16)
  
          if existing is not None:
              existing_samples, existing_sr = existing
  
              if existing_sr != sampling_rate:
                  raise ValueError('Different sampling-rate than existing data!')
  
              num_existing = existing_samples.shape[0]
              self._file[key].resize(num_existing + samples.shape[0], 0)
              self._file[key][num_existing:] = samples
          else:
              dset = self._file.create_dataset(key, data=samples,
                                               chunks=True, maxshape=(None,))
  
              dset.attrs[SAMPLING_RATE_ATTR] = sampling_rate